The present invention relates to methods of manufacturing structural tubes where the tubes are adapted to telescopingly engage, and more particularly relates to rollforming tube sections with stops and stop-receiving guide channels, using break-off methods that facilitate separation of the tube sections at an end of the rollformer.
There exists a prior art car jack (for lifting a vehicle to change tires) that uses, as part of its assembly for vertical strength, three telescoping tube sections that telescopingly mate together. The three tube sections are configured to longitudinally slide between a collapsed position where all three tube sections lie within each other, and an extended position where all three tube sections extend from each other (with only an inch or so of each tube section overlapping with the next tube section). The arrangement also permits the three tube sections to telescopingly slide together during assembly of the jack. The inner one of the three tube sections includes a first xe2x80x9coutxe2x80x9d dimple. The intermediate one of the three tube sections includes a first channel for receiving the first xe2x80x9coutxe2x80x9d dimple and also includes a second xe2x80x9coutxe2x80x9d dimple. The outer one of the three tube sections includes a second channel for receiving the second xe2x80x9coutxe2x80x9d dimple, and a third channel for receiving the first channel. A first xe2x80x9cinxe2x80x9d dimple is formed at an end of the first channel and is configured to abut the first xe2x80x9coutxe2x80x9d dimple to limit telescoping movement of the inner and intermediate tube sections. A second xe2x80x9cinxe2x80x9d dimple is formed at an end of the second channel and is configured to abut the second xe2x80x9coutxe2x80x9d dimple to limit telescoping movement of the intermediate and outer tube sections.
The above-described three tube sections are made by tube-forming techniques, where a tube section is initially cut to length and then stamped/re-formed to include the various xe2x80x9cinxe2x80x9d dimples, xe2x80x9coutxe2x80x9d dimples, and channels or keyways. However, the tube-forming technique is relatively costly for many reasons. It requires considerable multiple forming steps which result in considerable handling, tooling, and machinery. This in turn results in high labor and processing costs, high overhead, and high in-process inventory, all of which are expensive. Further, there can be considerable variation in the manufactured tube sections, particularly over time as dies wear, which can be problematic because the jack requires that the tube sections maintain tight tolerances that permit smooth telescoping movement without sloppiness or binding. For example, if one tube section has a diameter that is non-round or oversized, the mating tube section will either bind and not telescope, or it will be sloppy and unable to maintain a linear telescoping action such that it will buckle. Also, for example, if a dimple or channel is not properly formed, the dimples will not properly engage to limit telescoping movement, which will result in the jack potentially coming apart, resulting in an upset vehicle owner and/or potential safety hazard.
Methods of manufacturing tube sections are desired that solve the aforementioned disadvantages and that offer the aforementioned advantages, where the methods are capable of providing tube sections shaped for telescoping mating use, and are capable of producing the same at high volume, low labor, low cost, and with high dimensional accuracy.
In one aspect of the present invention, a method of manufacturing a structural tube comprises steps of providing a roll of sheet material, making transverse scoring lines in the sheet material, and rollforming a tubular shape from the sheet of material including forming a first longitudinal channel in the tubular shape. The method also comprises steps of welding the tubular shape into a permanent tube and breaking off tube sections of the permanent tube at the scoring lines and in line with an end of the rollformer.
In another aspect of the present invention, a method of manufacturing a structural tube comprises steps of providing a roll of sheet material, making transverse score lines in the sheet material and forming dimples in the sheet material. The method also comprises steps of rollforming a tubular shape from the sheet of material and forming a channel in the tubular shape.
In another aspect of the present invention, a method comprises steps of providing sheet material having a length and width, making non-uniformly deep transverse score lines on the sheet material and welding the tubular shape into a permanent tube. The method also includes steps of forming dimples adjacent the scoring lines with top and bottom dimpler rollers having top and bottom punches, the top and bottom punches being configured to form up and down dimples in the sheet material, and breaking off sections of the tube at the score lines.
In yet another aspect of the present invention, a method includes steps of providing sheet material having a length and width, making non-uniformly deep transverse score lines in the sheet material with a scoring roller, and rollforming the sheet material into a tubular shape. The method also includes steps of welding the tubular shape into a permanent tube, forming dimples adjacent the scoring lines with dimpler rollers having pre-scoring-line punches and post-scoring-line punches adapted to form dimples ahead of and after each scoring line, and breaking off sections of the tube at the score lines.
In still another aspect of the present invention, a method includes steps of providing sheet material having a length and width, and making transverse score lines on the sheet material. The method also includes steps of forming dimples with punches offset longitudinally forwardly and rearwardly from a position where the scoring lines pass under the punches, the punches being configured to form dimples in the sheet material at locations spaced longitudinally from the score lines, and continuously rollforming the sheet material into a tubular shape with a rollformer.
In still another aspect of the present invention, a method comprises steps of making transverse score lines on a roll of sheet material, forming dimples in the sheet material with punches at locations offset from a centerline of the sheet material and continuously forming the sheet material into a tubular shape. The method also comprises steps of welding the tubular shape into a permanent tube and breaking off sections of the tube at the score lines.
These and other aspects, features, and objects of the present invention will be further understood by reference to the following specification, claims, and appended drawings.